4
MAN3038-2
DISCOVERY PRODUCT GUIDE
4
Discovery Features- Smoke Detectors
4.1
Drift compensation:
Al l Discovery smoke detectors include compensation for sensor drift as part of the internal signal processing
algorithm. The algorithm will compensate for changes in sensor output caused, for example, by dust in the
chamber, and will therefore hold the sensitivity at a constant level even with severe chamber contamination.
This increased stability is achieved without significantly affecting the detector’s sensitivity to fire.
The compensation level is stored in the detector’s memory as a single value between 0 and 31. The normal
level, that is, with no compensation applied, is 16. Values above or below this indicate drift towards alarm or
away from alarm respectively.
For compensation values in the range 4 to 30 the detector is working within its allowable range. A value
which is less than 4 or greater than 30 results in a warning flag. A value of zero results in a fault signal.
ft Compensation Graph
The maximum compensation that can
be applied is 31. If further drift occurs,
the analogue values will simply
track
the drift and the detector will become
more sensitive.
Compensation values are stored in non-volatile memory and will be retained even if detectors are
disconnected. With few exceptions, it is possible to use the control panel to ascertain the level of
compensation applied at any time.
For the Discovery smoke detectors, the compensation algorithms are designed such that the detectors meet
the requirements of the European standard EN54–7:2000 in all response modes.
It is possible, through the protocol, to carry out a normalisation procedure which rapidly “updates” the drift
compensation. This facility should only be used after a compensated detector has been cleaned and instant
confirmation is required. (Otherwise the detector will automatically update itself within 24 hours).
Figure 1 – Drift Compensation Graph
